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Comment by staringback | Hacker News Reader

I am not convinced that gasoline detergents are anything more than marketing nonsense. You know what is already really corrosive? Regular gasoline.

I am curious to what the buildup you are referring to is, fuel injectors maybe? This might make sense on older multi-point fuel injection cars where their max power is like 60 psi, but on modern direct injection engines the fuel rail pressure is so unbelievably high that the sheer pressure would slice through any form of buildup. (My VAG engine for example, idles at ~700 psi and easily reaches twice that when moderate acceleration is demanded)

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If you're in a place with ethanol in the gas as an octane booster you're done right there.

Ethanol is fantastic at removing deposits. So much so when it was phased in 20 years tons of engines that had been running on non-ethanol blends had tons of trouble with deposits breaking loose and causing issues, especially anything with a carburetor that had built up deposits. The Ethanol broke down the deposits and then they'd get lodged in jets.

Modern engines seem way better at not building up deposits like you said, but things like Direct Injection also didn't become common (at least in the US) till Ethanol was also present.

The issue is not corrosion but buildup, which detergents help to disperse. High pressure itself doesn't cause high sheer forces during fluid flow, rather high velocity does. Any regions of the system with low velocity w.r.t. the surface could still experience buildups. Whether that happens in practice is certainly debated.

As a practical matter, it doesn't make a difference because almost everyone occasionally uses detergent gasoline (e.g., when that is the most convenient gas station).

I thought all gasoline had some detergents in it, not just the name brand stuff? I understood it as the name brand places add extra detergents or fancier additives, according to their marketing at least.

> High pressure itself doesn't cause high sheer forces during fluid flow, rather high velocity does

I am definitely not someone with experience in fluid mechanics, but I feel this goes against a layman's understanding of it? Could you provide some quick material on this claim so I could understand it? I already tried searching it but due to my limited knowledge of the subject I couldn't word my search to get the results I wanted.

What do you mean by "regular gasoline"? Are you referring to the different octane levels?

That wasn't clear - I just meant gas that's not top-tier detergent gas.

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